The present invention relates generally to the field of microelectromechanical devices, and, more particularly, to microelectromechanical thermal actuator devices.
Microelectromechanical systems (MEMS) may be used as alternatives for conventional electromechanical devices and systems, such as relays, switches, and switching arrays. In general, switches and switching arrays may be implemented using MEMS or non-MEMS devices. For example, a non-MEMS switching array may use an array of conventional latching electromechanical relays that are mounted on a circuit card. Unfortunately, the array dimension of such a switching array may be limited due to the physical size of the relays. Switching arrays may be designed, however, using multiple MEMS switches, which may be arrayed on a single die. This approach may allow for larger array dimensions and may also allow the switching array to be integrated with other on-chip circuit elements. Conventional MEMS based switching arrays, however, may use relatively large actuators to achieve mechanical row-column addressing. Moreover, conventional MEMS based switching arrays may be manufactured using relatively complex fabrication technology. Accordingly, there exists a need for improved MEMS based switching devices and switching arrays.
Embodiments of the present invention provide switches and switching arrays that use microelectromechanical devices that have one or more beam members that are responsive to temperature. For example, a microelectromechanical device comprises first and second beam members that have respective first ends connected to anchors, and that are also connected together. The first and second beam members are connected to a dielectric tether by a first tether anchor. The microelectromechanical device further comprises a third beam member that has a first end that is connected to an anchor and that is connected to the dielectric tether by a second tether anchor. At least one of the first and the second beam members are configured to elongate when the first and/or the second beam member is heated to a temperature that is greater than a temperature of the third beam member. By using two beam members to carry a control current to heat one or both of the two beam members, microelectromechanical devices, in accordance with embodiments of the present invention, may electrically isolate a control signal path defined by the first and the second beam members from a load signal path defined by a third beam member.
In other embodiments, the microelectromechanical device further comprises a tab attached to the dielectric tether anchor.
In further embodiments, the microelectromechanical device further comprises a substrate, and the anchors are attached to the substrate.
In still further embodiments of the present invention, the substrate has a trench etched therein that extends under at least a portion of the first and the second beam members. The trench may reduce the heat loss from the first and second beam members to thereby improve actuation distance of the first and second beam members for a given control power. The trench may also increase the signal isolation between the first and second beam members and the third beam member.
The present invention may also be embodied as a microelectromechanical switch that comprises a substrate, a pair of switch contacts attached to the substrate, and first and second actuators. The first actuator has a first end that is connected to the substrate, and has a contact connected thereto. The first actuator further comprises a first tab that is attached to the contact. The first actuator is operable to deflect in response to an electrical current. The second actuator has a first end that is connected to the substrate and has a second tab that is connected thereto. The second actuator is operable to deflect in response to an electrical current. The first and the second actuators are positioned such that the contact electrically connects the pair of switch contacts when the first tab engages the second tab between the pair of switch contacts and the second tab. Furthermore, the contact does not electrically connect the pair of switch contacts when the second tab engages the first tab between the pair of switch contacts and the first tab.
In other embodiments of the present invention, the first and the second actuators each comprise a first beam member and a second beam member.
In still other embodiments of the present invention, the contact comprises a first conductive region, which connects first and the second beam members of the first actuator, a second conductive region, and an isolation region that electrically isolates the first conductive region from the second conductive region.
The present invention may also be embodied as a switching array that comprises a substrate, a row signal path on the substrate that comprises a plurality of first switch contacts, and a column signal path on the substrate that comprises a plurality of second switch contacts. The switching array further comprises one or more first actuators that have an end that is connected to the substrate and have a contact, with a first tab attached thereto, connected thereto. At least one of the first actuators is operable to deflect in response to an electrical current. The switching array further comprises one or more second actuators that have an end that is connected to the substrate and have a second tab connected thereto. At least one of the second actuators is operable to deflect in response to an electrical current. The first and the second actuators are positioned such that the contact electrically connects one of the first plurality of switch contacts to one of the second plurality of switch contacts when the first tab engages the second tab between the switch contacts and the second tab. Furthermore, the contact does not electrically connect one of the first plurality of switch contacts to one of the second plurality of switch contacts when the second tab engages the first tab between the switch contacts and the first tab.
Although described above primarily with respect to device or apparatus aspects of the present invention, the present invention may also be embodied as methods of operating microelectromechanical devices, microelectromechanical switches, and switching arrays.